The design of buildings and other structures capable of withstanding earthquake events has been the research focus by engineers for many decades. A commonly accepted method for the design of seismic-resistant buildings and structures, however, has not been developed up to the present time. Fortunately, the traditional design methods, simply based on the static structural strength with impact factors to account for dynamic loads, have been reviewed and gradually replaced by novel methodologies over the last three decades. Concepts of structural element ductility and the importance of shear resistance have contributed to the ability to effectively design structural elements and systems that are resistant to dynamic loadings associated with earthquakes.
The use of passive and active systems has been proposed and implemented in an attempt to enhance the ability of the structure to resist and survive an earthquake event. Recent design methods have also been proposed in which seismic isolation technologies are utilized as a method to resist seismic loadings. One strategy implemented to date has been the addition of a base isolation system (usually a layer with low horizontal stiffness or sliding elements) between the base of the structure and ground. This system attempts to modify the fundamental frequency of the structure, thereby decreasing its acceleration response. The strategy of adding an isolation system between the base of the structure and ground will typically result in the structure with a much lower fundamental frequency than the original fundamental frequency of the non-isolated (fixed-base) structure. According to the acceleration design spectrum, a change in the fundamental frequency of a structure may reduce the acceleration response significantly, thereby enhancing the overall ability of the structure to withstand and survive the earthquake event. One significant drawback of a traditional seismic isolation system, however, is that the isolation system will usually have residual (permanent) horizontal displacements after earthquake events.
Better re-centering capability, supplementary dampers are desirable. Seismic isolation systems and methods discussed herein may utilize periodic materials, including 1D, 2D and/or 3D periodic materials.